<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title></title>
</head>
<body>
<div class="abc">
  <span class="red2">Red2</span>
  <span class="green">Gree2</span>
  <span class="red">Red1</span>
</div>

<style>


  .red, .green, .red2 {

    width: 200px;
    height: 200px;
  }

  .red {
    position: absolute;
    z-index: 0;
    top: 100px;
    left: 100px;;

    background: red;
    z-index: 1111;
  }

  .red2 {
    position: absolute;
    z-index: 0;

    background: red;
    z-index: 1111;
  }

  .green {
    position: absolute;
    z-index: auto;
    top: 40px;
    left: 40px;;
    background: green;
  }

</style>
</body>
</html>